Your cell phone is now useful for something other than playing Angry Birds. Researchers have found that a smartphone app can help scientists track temperatures in cities, enabling better planning for energy consumption.

Weather stations already record urban temperatures, but they’re expensive and only cover a small area. Cell phones, on the other hand, “could potentially collect worldwide temperature data at low cost in an automated fashion,” the study authors write in Geophysical Research Letters. Phones already contain temperature sensors to make sure that the batteries are not being charged when they’re too hot.

Using a smartphone app called OpenSignal, more than 530,000 smartphone users around the world collected 220 million battery temperature readings over the course of a year, the researchers report. With data from nearby weather stations, the team developed a model to convert those battery temperatures to air temperatures. The system isn’t perfect, since city-dwellers are often inside buildings. But future versions of the app could detect when the user is outside and discard indoor readings, the authors suggest. — Roberta Kwok | 29 July 2013